Pour a half cup of baking soda down the drain.
Pour a half cup of vinegar down the drain and cover the drain with a stopper or rag.
Boil a pot of water while the solution goes to work on the source of the clog. Wait at least 15 to 30 minutes.
Pour the pot of boiling water down the drain. The boiling water will flush the solution through the drain pipes.
Test the water flow. If the water appears to still be draining slower than normal, repeat the process. It may require repeating the process a few times to restore normal water flow.